We have developed an enzyme-linked immunosorbent assay (ELISA) for the detection of IgG antibodies against Helicobacter pylori (HP) using purified HP urease as an antigen. The urease was purified from ultrasonicated extract of HP by NaCl linear gradient system on DEAE-Sepharose 4B chromatography. Two molecular weight bands, 65kD and 27kD were observed on a SDS-PAGE gel in the purified urease sample. The urease antigen did not crossreact to rabbit antibodies prepared against Campylobacter coli and Campylobacter jejuni. Out of 93 gastric biopsy patients, sixty nine patients (74.2%) were positive in HP culture test. Serum HP antibody titers (AU: arbitrary unit) of HP culture positive and negative patients were 42.9 +/- 47.4 and 16.7 +/- 25.7 (mean +/- SD), respectively (p < 0.05). The ELISA system have sensitivity of 72.5% and specificity of 70.8%. We believe that the ELISA system is useful for diagnosis and monitoring of HP infection.